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首页> 外文期刊>Journal of Neurophysiology >Synaptically released glutamate does not overwhelm transporters on hippocampal astrocytes during high-frequency stimulation.
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Synaptically released glutamate does not overwhelm transporters on hippocampal astrocytes during high-frequency stimulation.

机译：突触释放的谷氨酸在高频刺激过程中不会压倒海马星形胶质细胞上的转运蛋白。

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In addition to maintaining the extracellular glutamate concentration at low ambient levels, high-affinity glutamate transporters play a direct role in synaptic transmission by speeding the clearance of glutamate from the synaptic cleft and limiting the extent to which transmitter spills over between synapses. Transporters are expressed in both neurons and glia, but glial transporters are likely to play the major role in removing synaptically released glutamate from the extracellular space. The role of transporters in synaptic transmission has been studied directly by measuring synaptically activated, transporter-mediated currents (STCs) in neurons and astrocytes. Here we record from astrocytes in the CA1 region of hippocampal slices and elicit STCs with high-frequency (100 Hz) stimulus trains of varying length to determine whether transporters are overwhelmed by stimuli that induce long-term potentiation. We show that, at near-physiological temperatures (34 degrees C), high-frequency stimulation (HFS) does not affect the rate at which transporters clear glutamate from the extrasynaptic space. Thus, although spillover between synapses during "normal" stimulation may compromise the absolute synapse specificity of fast excitatory synaptic transmission, spillover is not exacerbated during HFS. Transporter capacity is diminished somewhat at room temperature (24 degrees C), although transmitter released during brief, "theta burst" stimulation is still cleared as quickly as following a single stimulus, even when transport capacity is partially diminished by pharmacological means.
机译：除了将细胞外谷氨酸浓度保持在低环境水平外，高亲和力谷氨酸转运蛋白还通过加速谷氨酸从突触间隙的清除并限制递质在突触之间溢出的程度，在突触传递中发挥直接作用。转运蛋白在神经元和神经胶质中都有表达，但是神经胶质转运蛋白可能在从细胞外空间去除突触释放的谷氨酸中起主要作用。通过测量神经元和星形胶质细胞中突触激活的转运蛋白介导的电流（STC），直接研究了转运蛋白在突触传递中的作用。在这里，我们从海马切片CA1区的星形胶质细胞记录，并通过不同长度的高频（100 Hz）刺激序列引发STC，以确定转运蛋白是否被诱导长期增强的刺激所淹没。我们显示，在接近生理温度（34摄氏度）下，高频刺激（HFS）不会影响转运蛋白从突触外空间清除谷氨酸的速率。因此，尽管在“正常”刺激过程中突触之间的外溢可能会损害快速兴奋性突触传递的绝对突触特异性，但在HFS期间不会加剧外溢。转运蛋白的能力在室温（24摄氏度）下有所降低，尽管在短暂的刺激过程中释放了递质，但即使通过药理学手段部分降低了转运能力，“θ爆裂”刺激仍能像单次刺激后一样迅速清除。

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